1. Field of the Invention
This invention relates to a novel block copolymer and a copolymer composition comprising the same.
The block copolymer according to the present invention has properties of a thermoplastic elastomer and in addition, is excellent in affinity with a polar polymer typified by poly(methyl methacrylate) (PMMA), ABS resin and polycarbonate (PC), affinity with a non-polar polymer typified by polyethylene, weather resistance, solvent resistance and heat resistance. Said block copolymer can therefore be used singly as a molding or forming material and also can be added to another polymer as a modifier (ex. polarity imparting agent) or to a polymer composition comprising a polar polymer and a non-polar polymer as a compatibilizer.
2. Related Art of the Invention
As a readily moldable or formable elastomeric material, thermoplastic elastomers have been employed for various purposes such as automotive parts, electronic or electrical parts and construction or civil engineering materials. Particularly, a styrene-based thermoplastic elastomer (which may hereinafter be called "styrene-based TPE") typified by a polystyrene-polybutadiene-polystyrene block copolymer (SBS), polystyrene -hydrogenated polybutadiene-polystyrene block copolymer (SEBS) or polystyrene-hydrogenated polyisoprene-polystyrene block copolymer (SEPS) is a widely usable industrial material, because according to using purpose, the most suitable one can be selected from those different in stress-strain properties and the like, more specifically, those ranging from a vulcanized-rubber-like material to a plastic-like material [refer to, for example, Kouei KOMATSU, "Thermoplastic Elastomers--Basis, Application, Market and Future Prospects--" (published by Nikkan Kogyo Shimbunsha on Oct. 30, 1995)].
The styrene-based TPE, however, is poor in weather resistance and solvent resistance. As a thermoplastic elastomer improved in such properties, proposed are a block copolymer comprising a block of a hydrogenation product of a polybutadiene having a high 1,4-bond content and a block of a hydrogenation product of a polybutadiene having a high 1,2-bond content, and a block copolymer comprising a block of a hydrogenation product of a polybutadiene having a high 1,4-bond content, a block of a hydrogenation product of a polybutadiene having a high 1,2-bond content and a polystyrene block (which will hereinafter be called "hydrogenated 1,4-polybutadiene-based TPE", collectively) (refer to Macromolecules, 4(2), 152-154 (1971), U.S. Pat. No. 5,206,301, U.S. Pat. No. 5,216,074, etc.).
A polyolefin-based thermoplastic elastomer is prepared by copolymerizing ethylene and a long-chain .alpha.-olefin (ex. 1-octene) in the presence of a metallocene type polymerization catalyst (which elastomer may hereinafter be called "metallocene-based TPE"). This metallocene-based TPE exhibits its elastomeric properties by cohesion based on the crystallinity of its polyethylene moiety. Partly because it can be prepared at a low cost, it has started to be used widely for imparting a polyolefin-based material or recycled material thereof with tenacity.
Although the styrene-based TPE is inferior in weather resistance and solvent resistance as described above, its alloy with an acrylic resin which is, on the contrary, excellent in such properties has been proposed as a flexible material having good weather resistance and solvent resistance.
In addition, proposed are a block copolymer comprising a hydrogenated polymer block of a conjugated diene compound and a polymer block of a methacrylate ester, and a block copolymer comprising a hydrogenated polymer block of a conjugated diene compound, a polymer block of a methacrylate ester and a polymer block of an aromatic vinyl compound (which may hereinafter be called "methacrylate ester-noncrystalline hydrogenated diene-based block copolymer" collectively) (refer to European Patent Application Publication No. 0431706, U.S. Pat. No. 5,278,245, etc.).
The above-described hydrogenated 1,4-polybutadiene-based TPE or metallocene-based TPE cannot be used freely because of low affinity, and therefore, insufficient compatibility and adhesion to a polar polymer such as acrylic resin. The metallocene-based TPE is accompanied with the drawback that it has insufficient heat resistance and can exhibit only poor properties under high-temperature conditions compared with room-temperature conditions.
The above-described alloy of a styrene-based TPE with an acrylic resin is inferior in heat resistance, leading to low evaluation results in the test of compression set.
The above-described methacrylate ester-noncrystalline hydrogenated diene-based block copolymer is accompanied with such a drawback as inferior solvent resistance.